Cops suspect the deadly kidnapping of a Brooklyn slumlord was a professional hit ordered by one of the many creditors to whom he was deep in debt, sources told The Post.

Menachem “Max” Stark owed multiple people amounts ranging from tens of thousands to hundreds of thousands of dollars — and one apparently got fed up with waiting for the money, law-enforcement sources said Tuesday.

In addition, the two thugs who abducted and killed Stark during Thursday’s blizzard may have arrived from overseas to whack him, sources said.

Cops got “a flood of calls” from tipsters after Stark’s family on Monday increased the reward for information about his murder to $25,000.

Descriptions of his abductors “led us to believe that the suspects are not American. They could be from out of the country, possibly Europe,” one source said, declining to elaborate further.

Sources also said Stark’s widow told detectives that she saw a minivan matching the description of the kidnappers’ parked near their home about a week before her husband was grabbed from in front of his office.

In addition to racking up crushing debts, Stark ran rental properties riddled with code violations and sidelined as a loan shark, sources have said.

Undaunted, cops are interviewing gas-station workers and reviewing red-light camera videos between Brooklyn and the Great Neck, LI, Getty station where Stark’s burned body was found in a dumpster on Friday, sources said.

Also Tuesday, a lawyer for Stark’s business partner, Israel “Sam” Perlmutter, blasted a published report that said cops considered Perlmutter, 42, a “suspect” in Stark’s murder.

“He has nothing to do with it,” lawyer Henry Mazurek said.

Mazurek did not deny a Post report that Perlmutter said Stark owed more than $1 million to loan sharks, saying what he told police “is for the purpose of advancing their investigation.”